Abstract
Chemotactic migration of fibroblasts toward growth factors relies on their capacity to sense minute extracellular gradients and respond to spatially confined receptor-mediated signals. Currently, mechanisms underlying the gradient sensing of fibroblasts remain poorly understood. Using single-particle tracking methodology, we determined that a lysophosphatidic acid (LPA) gradient induces a spatiotemporally restricted decrease in the mobility of LPA receptor 2 (LPA2) on chemotactic fibroblasts. The onset of decreased LPA2 mobility correlates to the spatial recruitment and coupling to LPA2-interacting proteins that anchor the complex to the cytoskeleton. These localized PDZ motif-mediated macromolecular complexes of LPA2 trigger a Ca(2+) puff gradient that governs gradient sensing and directional migration in response to LPA. Disruption of the PDZ motif-mediated assembly of the macromolecular complex of LPA2 disorganizes the gradient of Ca(2+) puffs, disrupts gradient sensing, and reduces the directional migration of fibroblasts toward LPA. Our findings illustrate that the asymmetric macromolecular complex formation of chemoattractant receptors mediates gradient sensing and provides a new mechanistic basis for models to describe gradient sensing of fibroblasts.
Highlights
Chemotaxis is a fundamental process in many physiological and pathological events
We propose that lysophosphatidic acid (LPA) gradient sensing in fibroblasts is mediated by spatially organized, postsynaptic density-95/discs large/zona occludens-1 (PDZ) motif-mediated assembly of macromolecular complexes of LPA receptor 2 (LPA2) on the plasma membrane, which causes asymmetric intracellular Ca2ϩ signals to govern directional migration of fibroblasts (Fig. 8)
Chemoattractant receptors are uniformly distributed along the plasma membrane during random or chemotactic movement, even when cells are induced to reverse direction or turn by repositioning the micropipette filled with the chemoattractant cue [7]
Summary
Chemotaxis is a fundamental process in many physiological and pathological events. Results: An LPA gradient induces a spatiotemporally restricted decrease in the mobility of LPA2 indicative of its cytoplasmic anchorage to NHERF2, the cytoskeleton and PLC, which causes a gradient of localized Ca2ϩ puffs. Recent studies showed that depletion of extracellular Ca2ϩ disrupts the positive feedback loop that can be measured by either PI3K activity, actin polymerization, or protein kinase C (PKC) localization at the leading edge of polarized cells [24] Taken together, these observations suggest that Ca2ϩ gradients are indispensable to the positive feedback for gradient sensing of chemotactic cells. We report our findings that an asymmetric activation of LPA2 on the plasma membrane of fibroblasts elicits an asymmetric formation of macromolecular complexes of LPA2, NHERF2 (Naϩ/Hϩ exchange regulatory factor 2), and phospholipase C-3 (PLC-3) that, through an intracellular signal amplification mechanism, trigger the formation of spatially restricted, short lived, and high frequency Ca2ϩ microdomains (Ca2ϩ puffs), which govern the LPA gradient sensing and directional motility of fibroblasts
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
